Television system



Dec. 9, 1941. M. VON ARDENNE 2,265,657

' TELEVISION SYSTEM Filed April 18, 1959 INVENTOR MAM-WED z/oM ARDEN/v5 g i .ATTORNEYS Patented Dec. 9, 1941 UNITED STATES PATENT OFFICE TELEVISION SYSTEM Application April 18, 1939, Serial No. 268,460 In Germany March 29, 1938 2 Claims.

This invention relates to television systems and more particularly to television reproduction in natural colours and to stereoscopic television.

An object of the invention is to provide a novel apparatus for improving the quality of electro-.

optically produced images.

Another object of the invention is to provide improved means for producing in a receiver pictures with exactly coinciding differently coloured components and to produce multicoloured pictures free from flicker.

Another object of the invention is to provide a television receiver for reproducing multicoloured and stereoscopic images, which is simple in construction and includes preferably a cathode ray tube as a source of light. This cathode ray tube has preferably a screen, containing only a small number of light emitting areas, each area emitting light of a different wave length. Instead of the screen composed of areas of difierent light emitting properties, it is also possible to use a small number of stationary colour or polarising filters.

It is a further object of the invention to overcome the diificulties existing in all hitherto suggested methods for receiving multicoloured images.

According to the invention three differently coloured or two stereoscopic lines of a picture are produced in a receiver adjacent to each other. A picture of these lines is viewed or projected by means of an electrical or optical compensating device in such a manner, that the lines appear coincident for the observer. The compensating device is moved in synchronism with the scanning of the lines, so that the scanning component having a direction vertical to the direction of the lines is compensated. The lines do not only coincide geometrically on the viewing screen, but also with regard to time, so that there appears no flicker.

My experiments concerning the effect of the absolute number of picture elements per image on the definition show that with small numbers of picture elements the sharper and better defined black and white image is always preferred to the less defined coloured image or stereoscopic image. The experiments show however, that there exists a critical number of picture elements, beyond which a further increase in the number of picture elements results in only a slight improvement of the image and that this improvement is not as great as that when use is made of coloured or stereoscopic images. This number of picture elements is in the order of 100,000 with the standard black and white image. The television standard used to-day with 441 lines and 230,000 picture elements is high above this critical value, so that with the frequency bands in use at the present time it would be an improvement to change over to coloured or stereoscopic television images. This shows the great practical importance of workable technical solutions of this problem particularly on the receiving side.

For the reception of television images the cathode ray tube is being made use of in most cases. The cathode ray tube however makes special difficulties in this respect. It has been suggested to use a screen divided in adjacent differently coloured lines over its entire surface. This method has however the drawback, that the luminescent screen must be composed of lines of luminescent material corresponding with a precision of 1% with the lines drawn by the cathode ray. This precision cannot be obtained with the means to-day available for deflecting the cathode ray. In consequence of the limited precision of the deflection all methods must be excluded, in which the lines of the cathode ray must be brought to coincidence with lines mechanically produced on the screen. The same holds true with regard to stereoscopic images.

There exist methods in multicolour photography and in stereoscopic photography, in which three or two part images are projected unto each other. This method however cannot be used for television reception, because the images cannot be brought to coincidence with sufficient pre- 0151011.

The last mentioned difficulties do not exist, if the part images are produced one after the other on the screen of one and the same cathode ray tube, because then the errors in deflection are the same for all pictures, so that the pictures can be brought to coincidence. It is however difiicult to construct a screen for a cathode ray tube radiating in succession in three different basic colours. There remains therefore only the possibility to use three colour filters moving synchronously to the vertical deflection in front of a white luminescent screen, and in case light filters consisting for instance of gelatine attached to a motor driven disk are used, this method can be realised. It has however the drawback, that a pronounced flicker appears in the image, because the time between the changes of colour is too large. Even if the image periods per second would be increased it would be diflicult to eliminate flicker.

The same applies to the stereoscopic image reception, in which instead of the coloured filters a polarisation filter is used. The image must then be viewed through a polarising eye-glass.

All the drawbacks of these difierent methods are avoided according to the invention. Further features of my invention wil be apparent as will be specifically pointed out in the following description forming a part of the specification, but I do not limit myself to the embodi-v merits of the invention herein described, as vari" ous forms may be adopted within thescopepf the claims. Referring to the drawing? r 1 p 5 Fig. 1 shows the situation ofthelines on the 15 7 screen of a cathode ray tube.

Fig. 1A shows a side View of .theithree line .el e; ments disposed close to the bottom of. tl-iel cathvv ode ray tube 2.

Fig. 2 shows a section through an arrange- 2'0 men-tincluding a .cathoderay tube, a mir'ror wheeL-andaviewing:screen and Fig. 3. shows a similar arrangement for pro.- ducing stereoscopic images.

Fig. 1 shows the screen it of acathoderay tube 2. The left hand side of the figure shows a front view of the screenand the-rightihand sidea side view. The screen consists of three lines of. luminescent material A, B, C, eachline luminating upon impingement of the. cathode '30 ray in adifierent colour, for instance blue, yellow and red. The screen may for instance consist of zinc cadmium sulfide, the spectral .wave length of the different lineszof-thelscreen is obtained by using a differentncontent of cadmium sulfide,

so that each line luminates =in one ofithebasic colours. 1

Fig. 2 shows the complete. arrangement; The cathode. ray tube 2 contains a. lineldeflecting system H and. an auxiliary defiecting...system 3 40 moving the .ray verticallyto thedirection of the lines. A lens hissituatedinfrontof the cath- *line .C hasbeen scanned the deflecting. device :3

directs theray. again. to line :A and the .cycle is repeated. The deflection field 3 is synchronisedwith the frequencies. of the line deflecting field .in such a manner that its frequency is exactly one third of the .line frequency. Ac cording. to the invention the deflection of field 3 and the distancebetween. the. three lines is so arranged, that the. linesare-brought to coincide by the compensating device- In thepresent case the, mirrorwheel 4. is. used for building. .up the image. in the direction vertical to thelines. and at the same time, as compensating device. The 'e5 speed, of rotation of the mirror Wheel is so chosenwith respect to the image -.frequency, that themirror wheel. rotates once. for aewhole numberof images. The mirror. wheel rotates very slowlyandxdoes neither .produce vibrationswm nor-acoustical disturbances.

,, Duringthe .line period-the image. of line A 'mitted image.

are-scanned, the scanning of line A is repeated and a picture of line A is produced on the viewing screen 6 adjacent to the picture of the three foregoinglines;

Instead of the'mirror wheel a suitable device 'iorlproducing-the compensating movement of .the 'lig'ht.:.ray can be used. If a stereoscopic imageshall be produced only two lines are arranged on the luminescent screen. Fig. 3 shows such a device. The cathode ray-tube {2' contains .aescreen with two: lines A fand, i3, In front of the screentwo strips 8; and-9 .01 polarising material are arranged; which-produce;:a polarisation in two directions pernpndicular-toeach other. For separating and viewing .the'ztwo components a polarisingyfilter -;glass ;:1-,is; used. This. glass is arrangedin fron f. i fiyi; 0f the observer the, .polaris ing directions correspond to the directions of filters. 8-and-9 in front of the lines. The screen-mustbe made of. such a material, that no :depolaris-atien of the light. is. effected.

What I claim is: p

l. A television receiving- :systemadapted-to reproduce images of. light including agroup-of different characteristic lightcomponentg, coin prising a, pluralityof spatially displacedlightproducing elements each individuallycorrespending. to one "of said character sticcompone t means, including an electron. idischa-rg -device for successively scanning said, elements, for successively reproducing said characteristic eomponents, a viewing screemnand means-fersuperimposing the successively reproduced character- .istic. light components from said; elements; into a single line of light on said screen including said group of. characteristic components and; for

successively --spatially displacing subsequent groups. of, characteristic light cemponents to produce scansion-of said screen-and reproduction of. the transmitted, image. v I

2. A television receivingsystem adapted;-.to reproduce images {of lightincluding a' groupof difierent characteristic light; component-ps cinnpris n a. p u lity f spa a ly= d snleged hiproducing elements each individually corresponding to one of saidcharacteristic components, means, including-an lectron-discharge device for .zsuccessively --seanning saidelements, for successively reproducing said-light; components, a viewing screen,-andarota'hg-light deflecting member for superimposing .the successively reproduced; characteristic-lightcomponents sfrom saidcejlements' into :a singleline of li n said screen' nc ud ne a d; g oup, of

characteristic components, and for" successively spatially displacing subsequent. groups of characteristic light componentstofproduce scansion of said screen and reproduction-of the -.trans'- v w-acme.- 

